This invention relates to electromagnetic fuel injectors of the type that are used for injecting fuel into internal combustion engines.
The typical electromagnetic fuel injector is a lift sensitive device; in other words, the amountof fuel that is injected in response to a given pulse applied to the injector is related to the length of armature travel, i.e. lift. The greater the lift, the greater the amount of fuel injected for a given pulse width.
The timing of injection is usually a very important consideration in a fuel injection system, and because of wide-ranging fuel demands that can be imposed by an internal combustion engine, it is desirable for an electromagnetic fuel injector to have a suitable dynamic range. Dynamic range can be defined as the ratio of fuel flow at the maximum allowable pulse width to the fuel flow at the minmum operational pulse width, and pulse width as the length of time for which the injector is electrically held open. An injector that has a suitable dynamic range must be capable of delivering precise amounts of fuel in the range of engine speeds extending from idle to wide open throttle. At idle, a small amount of fuel must be precisely delivered, while at high speeds and loads, a larger amount of fuel must be precisely delivered. As engine speed increases, the time window within which fuel can be injected narrows, and therefore, a fuel injector must have a wide dynamic range in order to accommodate all engine operating conditions. The fuel injection task is particularly demanding in the case of a two-cycle engine.
One possible solution to meeting the wide range of engine demnand would be to use two injectors to span the range, one covering a lower portion of the range, and the other covering an upper portion. Disadvantages of such a solution include the need for extra parts and assembly. A preferred solution therefore is to use a single injector, and it is toward this objective that the present invention is directed.
Briefly, the invention comprises a fuel injector having a dual lift capability that endows the device with a wide dynamic range; for example ranges of up to 20:1 and 30:1 are contemplated. The lift of the injector is controlled by a second solenoid coil that is additional to the usual solenoid coil via which the injector is pulsed. When this second solenoid is not energized, the injector operates with lesser lift, but when it is energized, the injector operates with greater lift. The injector of the invention is characterized by an oganization and arrangement of component parts that are conducive to assembly, adjustment, and functional requirements.
Additional features, advantages, and benefits of the invention will also be seen in the accompanying drawing which discloses a presently preferred embodiment of the invention according to the best mode contemplated at this time for carrying out the invention.